1. Field of the Invention
The present invention relates to a fuel-vapor discharge structure for a fuel tank.
2. Description of the Related Art
Known fuel vapor structures have been used with fuel tanks for discharging fuel vapors. The discharged fuel vapor is routed to an engine intake system (see, for example, Japanese Patent Abstract 07-301353). The fuel vapor discharge structure includes a cylindrical main body having a two-way valve and a fuel cut-off valve mechanism. The outer periphery of the main body includes a flange portion. The two-way valve is arranged within the case main body and above the flange portion. The fuel cut-off valve mechanism is arranged within the case main body and below the flange portion.
The fuel vapor discharge structure is incorporated into the fuel tank by attaching the flange portion to the top surface of the fuel tank at the same location where the fuel cut-off valve mechanism is inside the fuel tank and the two-way valve is located outside of the fuel tank. Further, the upper portion of the main body has a vent port. A pipe connects the two-way valve and external canister to the vent port. The two-way valve has a positive pressure valve mechanism and a negative pressure valve mechanism. The two-way valve adjusts the pressure within the fuel tank in a predetermined range by ventilating the fuel vapor in both directions between the fuel tank and the canister. Further, the fuel cut-off valve mechanism prevents fuel from flowing into the canister even when there is change in the liquid level of the fuel tank.
In the fuel discharge structure above, the pipe connecting together the vent port and the canister is located above the top surface of the fuel tank. However, for engines having an engine generator or a general-purpose engine, the fuel tank is often arranged on the top of the apparatus with its top surface exposed to the outside. When the above-described fuel vapor discharge structure is used with such an engine, the pipe connecting the vent port to the canister lies across the top surface of the apparatus and is obtrusive when a user is operating or working on the engine apparatus.